The jabber plugin allows messages to be sent upon certain events. This is useful
but limited. In particular, the notification strategy option allows any one of
'all', 'failure' or 'change', but does not allow any combination of these.

It would be more generally useful in larger project teams if there were some
configurable matrix of jabber IDs agains the possible events that can cause a
message to be sent.

One simple way to implement this might be to to replace the existing 'targets'
and 'notification strategy' inputs with two targets fields: one for 'failure',
and one for 'change'. Also, add a third target field for 'success' notifications
(typically, a QA person might be interested only in successful builds for example).

A better way would be to have an extending list (e.g. similar to the extending
list of Subversion repository locations). This would effectively for a matrix:
each row would start with a jabber ID and would have tick-boxes for 'success',
'failure' and 'change'. It would be possible to add new rows to the table and
change or delete existing rows.